Oldhamite

minerals

troilite

niningerite

enstatite

Formula: CaS
Sulphide, galena group
Specific gravity: 2.58
Hardness: 4
Colour: Pale brown to dark brown, colourless to pale brown in transmitted light, tarnishes strongly on exposure to humid air (Mindat)
Common impurities: Mg,Na,Fe,Cu
Environments

Meteorites

Due to high melting point of 2450oC, oldhamite is an early nebular condensate; it may fill the latest interstices between silicates in enstatite chondrite and achondrite meteorites. Associated minerals include enstatite, augite, niningerite, osbornite, gypsum, calcite and troilite (HOM).
Terrestrial oldhamite is associated with pyrometamorpism, especially with coal fires. It is quite unstable in air, and hydrolysis makes it change into portlandite. It also occurs in anthropogenic blast furnace slag (Mindat).

Localities

At the type locality, the Bustee meteorite, Gorakhpur, Basti District, Uttar Pradesh, India, oldhamite occurs as single-crystal nodules, to 3 mm, in an enstatite chondrite meteorite. Associated minerals include troilite, osbornite, niningerite, gypsum, enstatite, calcite and augite (Mindat).

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